Low temperature low cost sulfuric acid alkylation process

ABSTRACT

Novel reactor design allows to provide a new and optimum sulfuric acid alkylation process which is operated at low temperature to provide all the benefits, with no complex mixing devices and cumbersome internals which have to be installed through manways. The novel art provided in this embodiment, provides novel Eductor mixing device, and auto refrigeration absorption rather than compression, and makes alkylate product which has a better octane, lower acid consumption and lower capital and operating costs. The reaction of C 3  to C 5  Olefins with Isobutane in the presence of 90 to 95% sulfuric acid concentration in this novel reactor design provides the low temperature (essentially under isothermal conditions) operation which has advantages over conventional processes of good product quality band low acid consumption. The process described in this embodiment has lower capital and operating cost by 40% compared to the conventional process and about 10% compared to new process/patents and provide much better flexibility and reliable equipment.

FIELD OF INVENTION

This invention relates to a simple reactor/mixer design for the sulfuricacid alkylation process where C₃, C₄ and C₅ olefins are reacted withisobutane to produce alkylate in the presence of Sulfuric acid catalyst.The conventional process has been practiced for a long time withmechanical propeller mixers and complex seals. The internal mixer andseals are working in a hostile environment (strong sulfuric acid whichis used as catalyst for the process) which is demanding. To provide themixing and tight emulsion one needs reasonable energy being provided toeach contactor/reactor and has been cause of lot of maintenance. Theprocess is practiced at certain temperature so as to keep the viscositylow and is not working at optimum temperature. Conventional processworks at higher temperature so as to keep the viscosity reasonable formixing. The Opex of the present conventional application together withcomplicated mixing device which has been known to require highermaintenance can be improved and more specifically present device of anEductor is being suggested. The total Capital and Operating costs can bereduced by the new device of Eductor by a factor.

Additionally a new concept of recovering the C₃/C₄ vapors from the autorefrigeration is being introduced which additionally saves capital costby either not having the compressor or in the case of revamps additionalequipment for absorption and desorption can be introduced which reducesthe cost of revamp by a large margin.

The alkylate product normally has reasonably good ROI based on theconventional process, but still the units require high investment. TheHF alkylation does not require refrigeration and acid regeneration so itis marginal better in that respect but is much more hazardous due to HFacids and is not readily acceptable environmentally and still capitalcost is little better.

BACKGROUND OF THE INVENTION

RHT alkylation process (RHT-Alkylation) of C₃/C₄/C₅ Olefins or mixcarbon number stream with these olefins, react with Isobutane in thepresence of Strong sulfuric acid as a catalyst to produce Alkylate(TMP), the reaction chemistry is similar to the conventional process,except the low cost contacting device providing optimum conditions forbetter product quality and low acid consumption without needingexcessive maintenance. The process operates essentially at isothermalconditions. The art of the reactor mixing device together with normalrefinery equipment makes it a simple operating system. The art of theinvention with eductor mixing device (or equivalent as a sparger andnozzles or similar in configuration) is able to operate at lowtemperature with auto refrigeration at isothermal conditions. Theadvantages of art has been already mentioned but will be summarized inthe Claims. The contacting device is unique that it can work withviscous fluids under operating conditions and without having any movingparts in the hostile environment in the reactor which makes it very costeffective. It does not have any other complex packing material which hasto be changed frequently and could be problem as regards to integrity ofthe system. The some of the reactor with internals as packed systemshave to obtain from a single source which is major drawback for anyprocess and are installed through a manway.

The reactor effluent is taken partly after settling as alkylate/C₄ mixand entrained acid. Due to the art in this embodiment utilized in theprocess, the unique mixing device in the reactor which is an Eductor,allows that the entrained acid can be removed from the hydrocarbon bysuccessive Coalescing devices as manufactured by York or equivalent toremove the acid from the hydrocarbon to ppm level as has been describedin Stratco articles in recent years they have been able to reduce theacid carry over to by three fold to few ppm to about <15 ppm. RHT havegone ahead and made the coalescing system to provide lower than 1 ppmlevel of sulfur in hydrocarbon product by changing and improving thedesign of Coalescers and also doing the coalescing under betterconditions i.e. higher temperature. This acid free hydrocarbon is sentto conventional alkylate recovery section after heat integration. Theheat integration system where hydrocarbons are heated to flash of C₄'shydrocarbon from alkylate between the coalescing stages, so that one canget better coalescing at higher temperature before the second orsuccessive stages of coalescing and separation. This location of thisflash drum is an important art employed to provide an efficient acidseparation at slightly elevated temperature of 40 to 300 F and heatintegration so as to reduce the load on compressor and are some of theclaims of this process.

The vapor from this flash drum can be sent to compressor intermediatestage or if the flash is done at higher pressure than can be condensedseparately and recycled to the reactor with olefin feed and isobutanerecycle after cooling with the cold alkylate. Alkylate is one of mostdesirable gasoline component as it is free of sulfur, aromatics andolefins Refiners are always looking at improving this alkylation processso as to reduce the acid consumption and utilities together withmaintenance costs. Due to the side reactions taking place due to theimpurities, during the alkylation process, acid soluble oils (conjunctPolymers; ASO) are produced which reduce the acid concentration andfresh acid make up is provided to overcome this requirement. The acidsoluble oil is sent to the acid regeneration unit. The cost of acidregeneration for low acid consumption unit is about 20% of the operatingcost of the alkylation unit. The RHT-Alkylation process at lowtemperature reduces the acid consumption and provides lower cost of acidregeneration apart from the major cost benefits of process mentionedabove.

SUMMARY OF THE INVENTION

This invention describes the alkylation of C₃, C₄ and C₅ mix streamswith isobutane and claims in the embodiment that the process uses aunique mixing device in the form of Mixing Eductor, or any similardevice like sparger or nozzles to mix the hydrocarbon stream withsulfuric acid to provide a much simpler and reliable process which canoperate at optimum temperature at just about isothermal conditions. Themixing device is a paradigm shift from the existing technologies whicheither have impeller and use excessive energy or complicated packingwhich has to be changed every so often. The eductor does not have anymechanical moving parts in the reactor and can be scaled to 15,000 b/din one reactor and even with field erected reactor the equipment canessentially be of any unit capacity with one train. But most of theClients would want a shop erected reactor and also for easier mobilityfor the unit. This provides scale of economy by a factor compared to theexisting art. As process can work at lower temperature with multipleeductors, it has multiple advantages compared to present art beingpracticed or being offered which will be illustrated in the claims, andis low Capex, low Opex option.

Another alternate can be provided with no C₄ compression system, whichcan be replaced with absorption system. As regards to Eductor it doesnot have to come from a single source, like internals and also has lowmaintenance costs. The unique concept of C4 auto refrigeration vaporscan be increased in pressure by Isobutane from the Deisobutanizeroverhead by the use of an ejector. This can be further increased inpressure by absorbing liquid, could be Iso-Octane product, heavy Naphthaor any other solvent which will absorb this C4 vapor stream. This vaporand the absorbing liquid can be separated by conventional distillationand C4 separation. This is major breakthrough of the process and is anart of the embodiment.

It has already been published in the literature and art of alkylation ofolefins with isobutane, and sulfuric acid as a catalyst under lowtemperature conditions (U.S. Pat. No. 5,095,168) and its benefits e.g.better product quality, low acid consumption. The present art ofinvention provides a low capex and opex based on the eductor patentedmixing device.

As has been published in the articles that in the papers by Stratco thatthe sulfuric acid has been reduced by three fold by the use ofcoalescers in the range of 5 to 7 wppm in hydrocarbon/alkylate stream,i.e. raw mix alkylate. The present embodiment with the help of majorimprovements in the design of coalescer have brought the sulfuric acidto below 1 wppm in the product going to de-isobutanizer and removed thealkyl sulfates as well. The process is shown in FIG. 3 but the coalescrscan be horizontal or vertical (preferably Vertical) and design underimproved conditions as explained earlier claims this as one of art ofthe process. If need be a small polishing absorber will be provided butwe do not find that necessary. Note that the vertical coalescers systemfor both the coalescers is preferred design and is being claimed as artof this patent.

As explained the chemistry is being used the same as by the conventionalprocess but major improvements are in:

-   a) Mixing device of Eductor-   b) The operating parameters of the reactor, low temperature,    isothermal conditions.-   c) Scaling of reactor-   d) Absorption and desorption of auto refrigeration vapors which    removes the need for additional moving item the compressors reducing    cost.-   e) Mixing with the eductor by putting the hydrocarbon at the pump    discharge in all proportions or putting in the side port and other    port for the reactor mixing is art of this embodiment and is.    Claimed by this patent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrates the Novel Mixing device, Eductor (or anyequivalent device as sparger or nozzles for mixing the reactants andcatalyst) or multiple eductors to agitate the reactants and catalyst, soas to get the reaction complete in shortest possible time and providesadequate interfacial area for the reaction. The art of mixing with theeductor in the embodiment of this invention by using recycle acid asmotive fluid for the eductor and Olefin Feed, recycle hydrocarbons,condensed C₄'s and recycle isobutane and contents of the reactor arepulled into the side chamber to mix the liquids, or can also be mixedwith the acid at the pump discharge using a inline mixer. The acid lineis put in through the bottom of the reactor so as to keep it inside(essentially acid is kept in reactor with minimum lines outside thereactor) as shown in the FIGS. 1 and 2 and this is part of the reactorinternal design and is claimed by this invention and eductor as mixingdevice is exclusive claim. The advantages of operating the reactorbetween 20 to 50 F, the art of low temperature operation has alreadybeen described in the U.S. Pat. No. 5,095,168.The present invention willwork at about 20 to 35 F, preferably at 25 to 27 F as close toisothermal conditions as possible due to inherent design of reactor andmixing device.

FIG. 3 describes the art of acid separation with Coalescer pads as hasbeen practiced by Conventional Licensers essentially forexpansion/revamp, with York or equivalent Coalescer pads in separationof acid and hydrocarbon. The hydrocarbon from the Primary Coalescervessel could be 5 to 50 wppm, the hydrocarbon from the primaryCoalescing step is sent to Finishing Coalescer after heating andflashing some of the hydrocarbons. The higher temperature will enhancethe coalescing of acid from hydrocarbon in the Finishing Coalescing stepand liquid product will have sulfur less than 1 wppm or lower. Thiscoalescer concept as has been experienced by York and Licensers canreduce the acid in the hydrocarbon and is being taken further to dryprocess concept based on the multiple coalescers and better separationnew design concept as a vertical Coalescer preferably but horizontal canalso be used, which provides reasonable saving in Capital cost and nocaustic waste. In the present art the claim of having the coalescing atthe finishing stage at higher temperature provides benefits of easieracid separation and this temperature can be 50 to 300 F but close to 80to 300 F so as to take advantage of the vaporization and reducing thecompressor load or can be condensed with water if lashed at higherpressure, and will have better efficiency as well. The major claim asstated above is to have the flash drum either before the finishingCoalescer or after, but to be at the optimum condition will be inbetween the coalescer stages so as to enhance acid separation fromhydrocarbon at higher temperature, and this practice is one of the claimof this process together with vertical coalescing step is a majorconcept of this claim.

FIG. 4 is a block Flow diagram of the whole process and describes theprocess completely, including the auto refrigeration step. Thepossibility of condensing the vapor from auto refrigeration in anabsorber is described in the FIGS. 5 and 6 as novel C₄ recovery systemfrom auto refrigeration. The back end after the reactor effluent flashdrum downstream of the polishing coalescer is similar to conventionalalkylation process for recovery of alkylate by distillation andrecycling the isobutane and removing the n-butane and light ends/propanefrom the unit.

FIGS. 5 and 6 is an alternate to the refrigeration vapor recovery viacompression of C4 auto refrigeration vapor (could be C3/C4 and C5 in anyproportion in the mixture) vapor absorption system. The vapor absorptionsystem will be cheaper and could be novel capex saving option and willbe an advantage in expansion of the unit where compressor is a bottleneck C₄'s can be absorbed in heavy Naphtha or in a special solvent oralkylate product. In the next column the C₄'s recovered and are recycledback to the alkylation reactor and the heavy hydrocarbon is recycled tothe absorber. The FIG. 4 shows unique utilization of ejectors toincrease the pressure of C₄ stream so as to have the absorption done at1 to 60 psig pressure ranges, preferably at 1 to 30 psig and preferablyclose to 15 psig as higher as practical to be cost effective. The uniqueEjector used to increase the pressure and absorption and desorptionsystem for C₄ recovery is one of novel claims of this patent. The motivefluid for the ejector could be liquid as shown in Figure or any othergas like isobutane from deisobutanizer or nitrogen.

DETAILED DESCRIPTION OF INVENTION

An aspect of this disclosure in this patent describes the process toalkylate C₃, C₄ and C₅ mixed olefins and isobutane stream is mixedvigorously in the presence of Sulfuric acid catalyst with novel eductordevice. Internal acid piping is provided to the ejector for the motivefluid. The alkylate is produced at low temperature which has a betterquality than the conventional process. The Capex and Opex are lower thanany other technology and it does not have any non reliable internals andalso installation of any internals in not time consuming. Essentiallythe process works under similar acid concentration as conventionalprocess in the range 89 to 95% but preferably around 90 to 92% toprovide the best quality product and low acid consumption, but at lowertemperature than conventional process at about 20 to 50 F but preferablyat 25 to 27 F in essentially isothermal conditions. The low temperatureis obtained by auto refrigeration by flashing the C₄ hydrocarbons. Acidto olefin molar ratio is kept around 45 to 180, preferably in the rangeof 45 to 60, to provide the desired alkylate reaction and quality. TheIsobutane to olefin molar ratio of 6 to 15 is desired. These ratio's arevery important and are controlled to provide the optimum conditions atthe low Opex. To provide the good mixing all the hydrocarbon streams aremixed and sent to the eductor where motive fluid of acid mixes all thestreams with acid catalyst and reactants to provide good selectivity,and undesirable reactions are minimized.

The disclosed methods and apparatuses can be understood by referring tothe attached figures, which are described in detail herein. It should beunderstood that the pipelines are being designated when streams arebeing identified and that streams are intended, if not stated, whenmaterials are mentioned. Moreover, flow control valves,temperature/pressure regulating devices, pumps, compressors, exchangers,drums and the like are understood as installed and operating inconventional relationships to the major equipment items which are shownin Figures/drawings and discussed hereinafter with reference to thecontinuously operating process of the this invention. All of thesevalves, devices, pumps, compressor and exchangers and the like, areincluded in the term auxiliary equipment. It is in the ability of one ofthe ordinary skill in the art to implement such auxiliary equipment, asneeded in view of the present disclosure.

FIGS. 1 and 2 discloses an embodiment of the disclosed the part ofreactor and Eductor system in the process. The reactor is a standaloneitem 1 and Eductor item 2 are the main part of this system. The acidsettles in the bottom of reactor, which is recycled by the pump backthrough line 8, where as the Olefin mixed stream (which includes all theC4 streams recovered and the olefin feed) are fed through line 6 toEductor to provide vigorous nixing of the acid and hydrocarbon. Packingand Demister pads are provided for obvious reason, which are clear tothe person who is accomplished in this art. As the reactor operates inthe range 1 to 10 psig range there is auto refrigeration due toevaporation of C3/C4 and some C5 hydrocarbons, which are taken out bythe line 3 from the Top. The reaction products together with someentrained acid and other components are taken for processing to otherequipment by line 7 as shown in the FIG. 1.

In the embodiment of this invention, following arts are beingspecifically practiced:

Operating the reactor at low temperature with unique reactor designwhere mixing is being done by the Eductor. Acid is supplied as motivefluid by an internal pipe in the reactor. The eductor provides adequatemixing so as to have reaction completed. The vapor is generated de toauto refrigeration and heat of reaction which is taken as vapor streamfrom the top of the reactor. The reactor effluent products which have 2045% alkylate is taken as a side draw with entrained acid which isseparated down stream.

The reactor is operated at about 1 to 10 psig pressure and 25 to 27 Ftemperature.

FIG. 3 illustrates the stream 7, which is the reactor effluent andcontains alkylate, C4 hydrocarbons and entrained acid is separated fromthe acid with multiple coalescers item 11 and 14 so as to have dryprocess. These coalescers are York type or equivalent to meet theproduct separation requirements. The Finishing Coalescer can be kept atthe optimum temperature to have better separation of acid andhydrocarbon in the range of 80 to 300 F. Recovered acid through line 9is recycled to the Reactor item 1 after separation in first coalesceritem 11. Where as line 10 takes the raw mix alkylate product throughheat exchangers and is flashed to remove some of C4's in item 12 flashdrum, through line 13 the C4 stream is taken for recovery. The bottom ofthe item 12 Flash drum is sent to item 14 where all the residual acid isremoved by finishing coalescer. The recovered acid is recycled to thereactor item 1 where as raw mix alkylate stream is sent to conventionalrecovery system where alkylate is separated from Isobutane and n-butane.

FIG. 4 illustrates an embodiment having the Block flow diagram of thewhole process. Some of the reactor and separation of acid/Hydrocarbonstream have been already described but one shows the full process bythis Figure. Acid strength is kept at about 90 to 92% and for that acidmake up made through line 24. Some the adjunct polymers (ASO) formed istaken out through the line 25, which is sent for acid regeneration. Asshown C4 Vapor from line 3 is sent to compressor or New absorptionsystem. Mixed Olefin Feed is mixed with all the other C4 streams fromthe unit before sending it to the reactor. The Reactor effluent fromItem 14 is sent for true alkylate recovery and is taken through line 20and line 21 separates the normal butane which is sent to OSBL, whereasIsobutane is recycled through line 22 to the reactor. Part of the C4auto refrigeration vapor after recovery is sent for lights/propaneremoval through item 19, line 26 and is sent to OSBL.

The process in this embodiment uses reactor effluent cold energy is usedto condense the De-Isobutanizer overhead and, or compressor dischargeafter cooling the total hydrocarbon stream recycled back to the reactor.This art has already been described in the U.S. Pat. No. 4,130,593 of1978.

FIGS. 5 and 6 in this embodiment provides option to absorb C₄'s producedfrom the auto refrigeration in the reactor through line 3 in HeavyNaphtha, special solvent or alkylate product. In this embodiment it isshown that the C4 streams pressure can increased to 15 psig or higherthrough line 33 by using Ejector with a motive fluids of Isobutane line32 and absorption liquid line 31 so as to make the absorption possible.In the next column the through line 35 the absorbed are sent forrecovery. The C4's are recovered through line 30 from HeavyNaphtha/Solvent or Alkylate (what ever is used for absorption of C4vapors) and C4 stream is recycled back to the reactor. The vent throughline 36 is used to control the absorption column control. The secondcolumn can be reboiled with LP steam and will be cheaper alternate toCompressor option and can also be used when revamping any unit where thecompressor is a bottleneck The back end of the unit is simplede-isobutanizer as one column system or two column system to separatethe Isobutane and n-butane from Alkylate. The straight chain olefinsprovide the slightly higher octane Alkylate from the Sulfuric acidalkylation compared to branched chain olefins, and the acid consumptionfor branched chain olefins is higher as well. So straight chain olefinsC₃, C₄ and C₅ are the preferred Olefin species.

REACTIONS

The reaction of olefins with isobutane provides Tri methyl Pentanes(TMP) which is the desired reaction products. The C₃ olefins providemore of di methyl Pentane (DMP) in the Alkylate and C₅ provide more ofC9 alkylate component giving lower octane product compared to C₄olefins. The straight chain olefins provide the slightly higher octaneAlkylate from the Sulfuric acid alkylation compared to branched chainolefins, and the acid consumption for branched chain olefins is higheras well. So straight chain olefins C₃, C₄ and C₅ are the preferredOlefin species.

In the Sulfuric Acid alkylation process, olefins and isobutane arereacted in the presence of Sulfuric acid catalyst at 20 to 60 F to formessentially TMP and some other products like Di methyl Hexanes (DMH) andDMP.

Alkylation ChemistryButylenes+Isobutane→TMPPropylene+Isobutane→DMPIt should be noted that even though in C₄ alkylation TMP has highconcentration over 60 to 70% in the alkylate product, but othercomponents are e.g. DMH and DMP, which are formed in the alkylationreaction.The side reactions can be postulated as follows:Polymerization olefin+olefin →Polymer C₆, C₈ and C₁₂ etcCrackingIn the reaction larger compounds are made which crack to make smallercompounds:C₁₁H₂₄ →C₆H₁₂+C₅ H₁₂Hydrogen Transfer reactionsThis reaction takes place by transferring hydrogen to olefin to makeparaffin. Essentially Isopentane is made in the reaction.2 C₄H₁₀+C₅ H₁₀ →C₈H₁₈ +C₅ H₁₂Esterification reactionSulfuric acid reacts with olefins to form small amount of di-butylsulfate, which is unstable at high temperature and is removed in thecoalescer so as to produce good quality product.DisproportionationThis takes place by rearrangement of the hydrocarbons to form differentmolecules from a larger hydrocarbon molecule.2 C₁₀H₂₂ →C₈HIs+C₁2H₂₆The relative reaction rates of olefins influence the product quality andrelative conversion rates can be postulated as follows:n-butene >i-butene>isopentenes>n-pentenes>propylene

From above one can deduce that one needs lower space velocity forpentenes and even lower for propylene compared to butylenes. In thepresent embodiment the novel reactor mixing device for alkylation wheremixed olefins stream and other recycle streams and excess of isobuteneis fed to the eductor and is mixed by acid being recycled as the motivefluid is new concept. The mixing is done in the eductor and in thereactor where predominantly TMP mixture, and 20 to 35% of other DMH, DMPand heavy compounds e.g. nonanes are produced.

As it has already been illustrated by prior art U.S. Pat. No. 5,095,168that working at lower temperatures around 10 to 50 F preferably at 25 to28 F, the selectivity to TMP is better providing better octane and alsolower acid consumption, the art here is being practiced under lowtemperature conditions. RHT-Alkylate process works at most desiredtemperature conditions, at isothermal conditions, which provide evenbetter results for selectivity. RHT-Alkylate process has much betteradvantage on Capex and Opex compared to competitive technologies and isless complex due to essentially reactor internal being just eductor.

Example

Feed, wt % Propane/Propylene 0.6 Isobutane 15.5 Isobutylene 14.72-butene 38.5 1-Butene 14.6 N-butane 15.8 C5's 0.3 Total 100.0

The above feed was used to produced alkylate and the results were verygood. The Road Octane was observed to be 94.5 to 95.0 with RON clear tobe 95.5 to 96.0 and MON Clear to be 93.5 to 94.0.

Based on flow sheet, the estimated total Installed cost of the unit isexpected to be 40 to 45% lower than the conventional process. The Opexis expected to be 35 to 40 lower than the conventional process. Thecapital cost saving can be realized even higher if auto refrigerationcompression is deleted and absorption of the C4's (lower molecularweight hydrocarbons) is done in heavy Naphtha, any solvents or alkylate.

1) Novel reactor design for mixing the reactants and the catalyst withthe Eductor, providing good interfacial area which makes the reaction togo to completion fast and provides good selectivity. A) The Eductordevice and any equivalent device like sparger or mixing nozzles arecovered by Eductor mixing. B) Provide internal Acid pipe in the vesselentering from the bottom and taking suction from the bottom as well asshown in the FIG. 1 and
 2. C) Operate the reactor at 20 to 50 Fpreferably at 25 to 27 F temperatures by having the auto refrigerationby evaporating the Light C4 components( C₃/C₄ and C5.components), andproviding isothermal conditions for the reaction which provide betterselectivity. D) Olefin Mix Feed, together with reactants, condensedhydrocarbons from the Refrigeration system, Isobutane recycle, Isobutanemake up are fed to the side chamber of the eductor and Acid is used asmotive fluid to mix the reactants and acid catalyst. E) Reactor scalingis easy and can be provided to larger scale from low capacity to largecapacity of 1,000 b/d or less to 50,000 b/d depending on fabrication ofthe reactor size in a single train system. 2) Well tested Coalescersystem (York or Equivalent) to remove acid from the hydrocarbon to lessthan 1 ppm. No caustic or acid wash required. Coalescer system designedto run in specific separation conditions so that all sulfur is removed.The Vertical Coalescers are preferred to horizontal and are claimed oneof the process invention. A) Feed to the de-isobutanizer flashed afterheating, to reduce the load on de-isobutanizer. The flash drum to beinstalled preferably in between coalescer stages so as to provide betteracid separation after heating the hydrocarbon Flash drum can beinstalled at most convenient location after the coalescing or in betweenthe coalescer stages depending on the requirements. The claim in thisart of having the finishing or multiple Coalescing stage at temperaturesof 40 to 350 F and most probably at 60 to 300 F is desired for betteracid and hydrocarbon separation. The art of Coalescing above 45 F isbeing claimed as an art practiced by this patent for improving thehydrocarbon acid separation efficiency. B) If required, flash drum canbe operated at a pressure where the hydrocarbons can be condensed withcooling water without loss of alkylate. Optimum case to be used for eachoperation. C) The reactor effluent to be used for cooling thehydrocarbon stream to the reactor and after this the cold energy fromthis stream should be used to cool other stream or to condenseDe-isobutanizer overhead. This has already been stated in the art ofU.S. Pat. No. 4,130,593. 3) Auto refrigeration vapor generated in thereactor either can be compressed and condensed or preferably adsorbed inthe Heavy Cat naphtha at the reactor pressure or after using an ejectorto raise the C4 vapor hydrocarbon pressure to about 1 to 50 psigpreferably at 1 to 10 psig. This is shown in the FIGS. 5 and 6 and thisart is claimed by this patent and is cheaper than compressor capex andOpex option. This novel idea is one of the major claim and paradigmshift in the technology. The absorption system can work at lowerpressure or at about 30 psig by increasing the C4 stream pressure byejector, and by using motive fluid as absorption liquid which could beAlkylate product, HCN, or any suitable solvent. The same fluid is usedfor enhancing the C4 stream pressure through the ejector and facilitatethe absorption process. The art of this patent also claims that thevapor motive fluids can also be used for the ejector to raise thepressure of C4 stream vapor generated by the auto refrigeration, theseVapor streams could be De-isobutinizer, or De-butanizer overheadproduct, or any other vapor like nitrogen etc. The concept of absorptionin lieu of compression by all these means is covered by this art whichis illustrated in this claim and has been shown in the FIGS. 5 and
 6. 4)The Isobutane to olefin molar ratio is to be kept between 6 to 15 toprovide the optimum conditions for best quality product and selectivity.The best ratio is around 8 to
 11. This includes recycling some of thereactor effluent to the reactor with the entire hydrocarbon recyclestream and feed olefin, as mentioned in the patent above. A) Acid toolefin molar ratio is kept around 10 to 300, preferably in the range of45 to 60, to provide the desired alkylate reaction, selectivity andquality. B) As has been practiced in the art of alkylation one or twofractionation columns are used to separate the product. Thede-isobutanizer as a single column system or two column system, whereisobutane, alkylate and N-butane can be fractionated to the desiredspecification is normally practiced. C) The unit Coalescing system willremove the acid and any di-alkyl sulfate formed but small bauxite orsimilar sulfur adsorption system may be provided for polishing thesulfur removal system. D) The cold energy available from the autorefrigeration absorption liquid can be used to Condense De-Isobutanizerand De-butanizer overhead product, provided major saving cooling water.As mentioned earlier this saves major capital for compression and allthe associated equipment with the compressor. This is one of the majorparadigm shifts in the art to save the capital cost by absorptiontechnique. E) RHT-Alkylation process in this invention provides easyrevamp solutions in the Following area: Capacity by adding a Reactor. Byusing absorption system where Compressor is a bottle neck. 5) In thispatent, the art of part of the mix hydrocarbon feed (including olefin)can be split before feeding it to the side port of the Eductor, and ismixed with motive fluid at the pump discharge by installing an inlinemixer to provide enhanced mixing. 6) This art of putting some or all thehydrocarbon feed feeding to motive fluid pump discharge is especiallydesired for the propylene alkylation to provide higher over all spacevelocity (OSV). 7) The art in this patent also takes care of the bestpractices of Coalescing of Acid/Hydrocarbon in a preferably horizontalcoalescer, but not limiting it to that option, so to optimize if theVertical coalescer provides best option than one will be using theoptimum option for this application. 8) Provide the auto refrigerationvapors absorbed in alkylate Heavy naphtha or any solvent (claiming theabsorption application instead of compressor if so required and ischeaper). 9) Provide the flash from item 12 to the de isobutanizer at ahigh enough pressure so as to condense the C4 hydrocarbons either withwater or with cold process fluid if available, this will save compressorenergy, and is claimed by this patent and art as described here.